1. Field of the Invention
The present invention relates generally to ascertaining the dimensions of three-dimensional objects, and, more particularly, to determining the length, width and height of cuboidal objects while such objects are in constant linear motion as, for example, on a conveyor belt.
2. State of the Art
Millions of packages per year are handled and shipped by United Parcel Service, Federal Express, and many other smaller courier and delivery services as well as by the United States Postal Service. These packages originate with federal, state, and local government as well as private businesses of all sizes. In many instances the charges by these carriers to their customers are based on the so-called "dim-weight" or "dimensional weight" (DW) of the object being shipped. DW is a fictitious dimension based on length (L) times width (W) times height (off) in inches divided by a standard agency- or association-recognized divisor or dimensional weight conversion factor, commonly 166. Thus, the DW equals L.times.W.times.H divided by 166. The "166" divisor or conversion factor has been recognized and adopted by the International Air Transport Association (I.A.T.A.). Even if an object or package is of an irregular configuration, the dim weight, using the longest measurement each of length, width, and height, is still utilized for billing purposes. The volume computed by multiplication of object length times width times height may hereinafter be termed the "cubic volume", "spatial volume", or simply the "cube" of the object.
The measurements of the objects shipped are also critical so that the carrier can accurately determine the number of trucks, trailers, or other vehicles which will be required to transport goods to their destinations and so customers and carriers can accurately estimate their warehousing and other storage needs.
In addition, article weight and measurements are also used to determine and predict weight and balance for transport vehicles and aircraft and to dictate the loading sequence for objects by weight and dimensions for maximum safety and efficiency.
Further, if orders of any items are to be packed into boxes, knowledge of object weight and dimensions is useful for selecting box size and durability.
The assignee of the present invention has been instrumental in developing quick, accurate means and methods for determining the dimensions and the cubic volume or spatial volume for packages and other objects in a commercial or industrial setting. For example, U.S. Pat. No. 5,042,015, assigned to the assignee of the present invention, discloses a practical and commercially successful means and method for object measuring. However, the patented method and apparatus requires, for measurement of moving cuboidal objects, that the sides of the objects be aligned parallel and perpendicular to the path of movement. Thus, there existed a need for a system for measurement of skewed cuboidal objects.
One such system for measurement of the dimensions of skewed objects (of any shape) is described in U.S. Pat. No. 4,773,029. The system of the '029 patent, however, senses the apparent dimension of the moving object solely through use of infrared emitter-receiver rays and establishes the true length and width of an object by periodic measurements which provide "slices" of the object, the slices then being summed to provide a horizontally planar footprint of the object from which the true length and width are determined. The inventors have no specific knowledge as to whether a commercial embodiment of this system in fact works as described in the patent, but the system's advertised cost makes it prohibitively expensive, beyond the capabilities of many businesses, and a financial burden on those few companies able to afford it.
U.S. Pat. No. 5,105,392, assigned to the assignee of the present invention, provides an alternative to the system of the '029 patent for measuring skewed cuboidal objects. The '392 patent discloses and claims a method and an apparatus for determining the actual length and width dimensions of a linearly moving object with a rectangular footprint by determining apparent length, apparent width, and the distance between an object corner facing to the side of the travel direction and the trailing edge of the object. These measurements are then employed to determine the actual object length and width by trigonometrically-based mathematical equations. The methodology as described in the '392 patent has been proven to be sound, as have the mathematical relationships, but the apparatus as described in the application employed to obtain the dimensions has been found lacking as to the accuracy desired by the assignee.
Yet another patent, U.S. Pat. No. 5,220,536, also assigned to the assignee of the present invention, employs a different, light-curtain-based apparatus to determine the length and width of a skewed cuboidal object and employs the mathematical relationships previously developed for the '392 patent.
Another light curtain-based, in-motion dimensional measuring system is also offered commercially by the assignee of the present invention as the CubiScan.RTM. 200.
One problem common to all of the commercially offered in-motion dimensioning systems on the market is the necessity for a gap or "break" in the conveyor system on which the objects to be measured are moving. Thus, all of the state of the art systems for in-motion measuring of objects, cuboidal or otherwise, require a more or less custom installation and must be installed in conjunction with a new conveyor system, or at least a segment of an existing conveyor system must be scrapped and a new system or portion with the requisite "break" installed. A further disadvantage of all commercially offered in-motion dimensioning systems is their high cost and the already-alluded-to difficulty of installation, particularly in existing warehouse, shipping, or other storage facilities which are not initially designed to accommodate these systems and in which space may be at a premium. Thus, there is a need for an accurate, relatively inexpensive, easily installed dimensioning system which can be integrated not only with newly-installed conveyor systems, but can be integrated with the majority, if not all, existing, constant-speed belt or roller type conveyor systems.
The inventors have recognized that well in excess of 90% of all packages and other objects which are commercially shipped in the course of normal business and industry are in fact cuboidal in shape, that is to say, that such objects have a parallel top and bottom and two pairs of mutually parallel sides, each pair of sides being at a 90.degree. angle to the other pair and all of the sides being at a 90.degree. angle to the top and bottom of the object (i.e., they form a Parallelepiped). This regular and predictable configuration, therefore, is susceptible to a relatively simple and inexpensive means and method developed by the inventors for measuring length and width while the object is moving linearly at a substantially constant rate. The height of the object may be determined by any one of a number of approaches, including reflective ultrasound or the use of a light curtain.